Bs-->K(*)0 K(*)0 CP asymmetries: golden channels for new physics searches

We point out that time-dependent CP asymmetries in B_(s)-->K(*0) K[over](*0) decays probe the presence of new physics in b-->s transitions with an unprecedented theoretical accuracy. We show that, contrary to the case of B_(d)-->phiK_(S), it is possible to obtain a model-independent prediction for the coefficient S(B_(s)-->K(*0) K[over](*0)) in the standard model. We give an estimate of the experimental precision achievable with the next generation of B physics experiments. We also discuss how this approach can be extended to the case of B_(s)-->K[over](*0) K(0), B_(s)-->K(*0) K[over](0), and B_(s)-->K(0) K[over](0) decays and the different experimental challenges for these channels.     

Comparison of Coated and Immobilized Chiral Stationary Phases Based on Amylose tris-[(S)-α-Methylbenzylcarbamate] for the HPLC Enantiomer Separation of α-Lipoic Acid and Its Reduced Form

The couple of chiral sulfur compounds α-lipoic acid (ALA)/α-dihydrolipoic acid (DHALA) has attracted considerable attention in recent years owing to its remarkable anti-inflammatory and antioxidant properties. It is well known that the chirality of the C6 plays a key role in determining the biological activity of ALA. The natural occurring (R)-ALA enantiomer is an essential cofactor for key oxidative metabolism enzyme complexes and, after oral administration of the racemic mixture, it shows higher plasma concentration than (S)-ALA. Differently, the in vivo enantioselective action difference between the enantiomers of DHALA has not yet been studied. This lacking is perhaps due to the unavailability of analytical methods capable of determining the enantiomeric composition of biological samples during pharmacokinetic and pharmacodynamic events. In the present work, the direct and baseline enantioresolution of both chiral acids by HPLC on two amylose-derived chiral stationary phases is presented. The proposed chiral enantioselective protocol, therefore, does not require pre- or on-column derivatization. The performance of the coated Chiralpak AS-H CSP and the new immobilized Chiralpak IH-3 CSP, which have the same chiral selector amylose tris-[(S)-α-methylbenzylcarbamate], were compared using conventional normal-phase mobile phases containing ethanol or 2-propanol as alcoholic solvents and a fixed percentage of trifluoroacetic acid. Nonconventional eluents containing dichloromethane, ethyl acetate, and 2-methyltetrahydrofuran as organic cosolvents were applied in the separation of the enantiomers of two carboxylic acids on the immobilized Chiralpak IH-3 CSP. The effect of the column temperature was carefully evaluated in order to improve enantioselectivity. Adequate amounts of enantiomers were isolated by an analytical-size Chiralpak IH-3 column and submitted to chiroptical measurements. The absolute configuration assignment of the isolated enantiomers was determined by a multidisciplinary procedure based on the comparison of the experimental and calculated chiroptical properties.     

High-performance liquid chromatographic separation of enantiomers and diastereomers of 2-methylcyclohexanone thiosemicarbazone, and determination of absolute configuration and configurational stability

Simultaneous HPLC diastereo- and enantioseparations of 2-methylcyclohexanone thiosemicarbazone (2-MCET) were accomplished on coated- and immobilized type polysaccharide-based chiral stationary phases (CSPs). The identification of all stereoisomeric forms and their stereochemistry were achieved by combining theoretical, HPLC and chiroptical data. The stereochemical stability of the target compound was studied by classical off-column and dynamic HPLC kinetic procedures and the influence of different parameters such solvent, TFA concentration and temperature on stereoisomerization process was evaluated. The findings obtained by chromatographic and kinetic experiments were used to develop a simple method to convert the racemic form of 2-MCET into a single enantiomer.     

Nitrosonium complexes of resorc[4]arenes: spectral, kinetic, and theoretical studies

Resorc[4]arene octamethyl ethers 1-3, when treated with NOBF4 salt in chloroform, form very stable 1:1 nitrosonium (NO+) complexes, which are deeply colored. The complexation process is reversible, and the complexes dissociate and bleach upon addition of methanol or water, to give the starting macrocycles. Resorc[4]arenes 1 and 2 are in the same cone conformation, but with different side-chains, whereas 3 possesses a different conformation (chair), while bearing the same side-chain as 2. Kinetic and spectral UV-visible analysis revealed that NO+ interacts with resorc[4]arenes 1 and 2 both outside and inside their basket, leading to complexes with two absorption patterns growing at different rates, one featuring high-energy bands (HEB) within the near-UV zone, and the other one low-energy bands (LEB), attributed to charge-transfer interactions, within the visible range. The presence of ester carbonyl groups in 2 strongly drives the NO+ cation outside the resorcarene. Resorc[4]arene 3 showed a spectral pattern pointing out a clear involvement of the ester moieties in the NO+ entrapping, beside the formation of significant charge-transfer interactions. 1H NMR spectroscopy and molecular modeling clearly supported these findings.     

Power spectrum and Fisher–Shannon information plane analysis of tidal records

The time dynamics of tidal fluctuations measured in three sites in Bahia Blanca Estuary (central Argentina), Ingeniero White, Puerto Belgrano and Torre Mareografica, are analyzed. To investigate the time series of the tidal waves we used two different approaches: the power spectral density (PSD) and the Fisher–Shannon (FS) information plane. The PSD permitted: (i) the identification of diurnal, semi-diurnal and higher frequency cycles in all the three tidal signals, and (ii) the detection of two different dynamical regimes (scaling and white-noise), involving respectively timescales lower and higher than about 2–2.5 days. The FS method, which allows to gain insight into the complex structure of a time series, quantifying its degree of organization and order, was applied to the residual tidal series (after removing the main cycles) and permitted to identify a period of low organization in the tidal signal measured at Puerto Belgrano.     

Stereolability of dihydroartemisinin, an antimalarial drug: a comprehensive kinetic investigation. Part 2

Artemisinin or qinghaosu has now largely given way to the more potent dihydroartemisinin (DHA, 1) and its derivatives in the treatment of drug-resistant malaria, in combination with other classical antimalarial drugs. DHA is obtained by NaBH(4) reduction of artemisinin and contains a stereochemically labile center at C-10, which provided two lactol hemiacetal interconverting epimers, namely 1α and 1β. In the solid state, the drug consists exclusively of the β-epimer; however, upon dissolution, the two epimers equilibrate, reaching different solvent-dependent ratios with different rates. Such equilibration also occurs in vivo, irrespective of the isomeric purity at which the drug would have been administered. The aim of this study was then to achieve an in-depth understanding of the kinetic features of the α/β equilibration. To this purpose, free energy activation barriers (ΔG(?)) of the interconversion were determined as a function of both general and specific acid and base catalysts, ionic strength, and temperature in different solvents by dynamic HPLC (DHPLC). In hydro-organic media, the dependence of ΔG(?) on temperature led to the evaluation of the related enthalpic and entropic contributions. Theoretical calculations suggested that the rate-determining step of the interconversion is not the ring-opening of the cyclic hemiacetal but the previous reversible deprotonation of the individual epimers (base-catalyzed mechanism). The whole findings may contribute to shed some light on the mechanism of action and/or bioavailability of the drug at the molecular level.     

Stereolability of dihydroartemisinin, an antimalarial drug: a comprehensive thermodynamic investigation. Part 1

Artemisinin (Qinghaosu, 1) is a sesquiterpene lactone endoperoxide isolated from Artemisia annua L. that Chinese herbalists have traditionally used to treat malaria. Reduction of artemisinin by NaBH(4) produced dihydroartemisinin (DHA, 2) and yielded a new stereochemically labile center at C-10, which in turn provided two lactol hemiacetal interconverting epimers, namely, 2α and 2β. With the aim of fully investigating the thermodynamics of interconversion, we gathered the relative abundance of the two epimers within a wide variety of solvents and rationalized the results by linear solvation energy relationships (LSER) analysis. Beside the difference in polarity, the better stabilization of 2α in polar solvents was found to be significantly related to its greater acidity with respect to 2β, which was estimated by two independent theoretical approaches based on molecular modeling calculations and empirical data, and supported by (1)H NMR measurements. On the contrary, differential effects of cavitational energy have been highlighted as interactions strongly responsible for the small values of equilibrium constant measured for the β ? α process in the less polar media. Determination of forward and backward epimerization rate constants in seven media, clearly differing in both permittivity and capacity to be H-bond donors, indicated that, in the spontaneous process, the transition state of the rate-limiting step develops a significant degree of anionic character, as typically happens in the base-catalyzed breakdown of hemiacetals.     

An SPE Method for the Concurrent Extraction of Organochlorine and Phenoxy Acidic Pesticides in River Water

We present the validation of a multiresidue method for the concurrent SPE of organochlorine (OCP) and phenoxy-acidic pesticides (PA) in river water. The two classes of compounds show very different chemical characteristics. The analyses were performed by gas chromatography?Cmass spectrometry and by liquid chromatography?Celectrospray ionization?Cmass spectrometry. The method was validated at three different concentrations: method limit of quantitation, 0.5 and 5 ??g L^?1. The recoveries were in the range 65?C135% for all the target compounds and in the range 83?C113% with RSD <20% for most of them at all the concentrations tested. The method showed good accuracy, precision, and sensitivity, and allowed the analysis of the selected pesticides at a concentration lower than that required by the EU current legislation for surface water [1]. The single-step procedure reduced artifacts, matrix effects, and speeded up sample preparation.     

Synthesis of triaryls: hydroxy and amine dinaphthyl and diphenanthryl aryls by one-pot electron-transfer nucleophilic substitution reactions

A new one-pot synthetic route to achieve the preparation of hydroxy and amine binaphthyl and biphenanthryl aryls is here reported. This approach involves the reaction of 1,4-bromoiodobenzene, 4,4′-diiodobiphenyl, and 1,4- and 1,5-diiodonaphthalene with the anions of 2-naphthylamine, 2-naphthol, and 9-phenanthrylamine under irradiation in liquid ammonia. The reactions proceed to afford triaryl derivatives in moderate to good yields (∼45% of 1,4-phenylene- and 1,4-naphthylene-1,1′-dinaphthalen-2-ols as well as 1,4-phenylene-1,1′-dinaphthalen-2-amine and 10,10′-diphenanthren-9-amine). Lower yields (27%) of polyaryl derivatives are obtained by reaction of 4,4′-diiodobiphenyl with anions of 2-naphthol and 9-phenanthrylamine.     

A turbulent data analysis in the Antarctic boundary layer

Summary Data collected by the Institute of Atmospheric Physics of CNR (Italy) during the 1991 Italian Antarctic expedition are used for the development of Earth-air-sea interaction studies. In this paper wind and temperature data obtained by a digitized ultrasonic anemometer-thermometer describe the temporal, statistical and spectral turbulence behaviour in the surface atmospheric boundary layer at different wind conditions and in morphologically different sites. The vertical momentum and thermal fluxes, evaluated through the direct method, are found to be strictly dependent on the local stability condition recorded during the measurements. The examination of the velocities and temperature probability density functions confirms the Lumley and Panofsky hypothesis on the influence of both velocity components on temperature fluctuations. A multichannel spectral analysis confirms the obtained results for the low-frequency range. The authors of this paper have agreed to not receive the proofs for correction.